Blazing a trail

By Jonathan Knight

ONE night in 1922, on a freighter from Amsterdam bound for the Spanish port
of Alicante, the Dutch artist M.C. Escher witnessed one of the marvels of the
sea. The first mate walked him forward to the ship’s bows to show him glowing
dolphins.

The sea was dark except for an intense bioluminescence surrounding the ship
and illuminating its wake, and just ahead Escher saw the luminous blue shapes of
dolphins swimming in the bow wave. “An unforgettably beautiful spectacle,” was
how he described it in his diary, “they shot forwards leaving a tail of light
behind them.”

The following day, he sketched what he had seen, and a few months later he
turned the sketch into a woodcut called “Dolphins in a phosphorescent sea”.
Escher often said he felt closer to science than art, but he had no idea that
his woodcut would later attract the interest of marine biologists trying to
understand how dolphins swim. Nor could he have imagined that the same bright
light he saw that night would one day help scientists to develop artificial
hearts, design incubators for human cells, and even understand the weather.

What all of these challenges have in common is the movement of fluids—a
remarkably difficult thing to study. Any fluid—be it water, wine or
air—looks much the same whether it’s still or swirling. Just as sailors
look at clouds, flags and ripples on the water to judge the wind, fluid
dynamicists need tricks to help them see how fluids move. They can inject dye
into a stream of water, or track moving particles with …

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